A Study On The Occurrence Of Mercury And The Chemical Thermodynamic Calculation Of Mercury During The Mild Thermal Upgrading Process Of The Typical Coal From Guizhou Province

Now the society's energy production is still rely on the coal combustion in very great degree. The environmental pollution question which caused by the coal combustion arouses more and more people's concerns, especially the harmful trace elements of pollution. It has been proved by the research that the mercury emissions relate not only to the mercury content in the coal, but also to the distribution and the occurrence of mercury in the coal. The method of mild thermal upgrading before coal combustion has been proved to be an efficient way to remove mercury and sulfur from the coal samples. It also has been proved by the research that the mercury removal efficiency during mild thermal upgrading related to the occurrence of mercury in the coal. For these reasons, the study on the mercury removal efficiency must be combined with the research on the occurrence of mercury in coal. And the chemical thermodynamic calculation is an efficient way to predict the speciation of mercury and sulfur during mild thermal upgrading.Two coal samples with high mercury and sulfur contents from Guizhou Province were selected in this study. Firstly, the contens and occurrences of mercury and sulfur in the two typical coal samples were studied by a series of experiments. The studies show that the mercury in LZ coal sample may be associated with pyrite, and the form of sulfur was pyritic sulfur. The mercury in ZY coal sample may be associated with kaolinite, and the form of sulfur was organic sulfur. Then the mild thermal upgrading experiment was taken out by using a horizontal tube furnace. The mercury and sulfur releasing characteristics of the two coal samples during mild thermal upgrading were studied under low oxidizing atmosphere and N2 atmosphere. The study showed that the low oxidizing atmosphere can promote the removal of pyritic sulfur and the removal of mercury within the temperature range from 350-400℃. But the promotion of the removal of organic sulfur by low oxidizing atmosphere was not observed. Finally, FactSage5.4, the software of chemical thermodynamic calculation was use to predict the species of mercury and sulfur in flue gases during mild thermal upgrading. The study showed that the atmosphere, S/Cl and pressure had a significant influence on the species of mercury in flue gases.